The present invention relates to the measurement of the level of a process fluid in a container. More specifically, the invention relates to measurement of level of process fluid based upon pressure.
Many industrial processes require the monitoring of various process variables related to a process fluid. One example process variable which is monitored is the level of a process fluid within a container. This information can be used for maintaining an inventory of the process fluid, or can be used in controlling operation of a process.
Various techniques are known for measuring the level of process fluid in a container. One technique for measuring process fluid level is based upon a pressure, for example, a differential pressure. In one example configuration, a side access port is provided near the bottom of the container. The pressure of the process fluid at this location is measured using a pressure sensor. For example, an isolation diaphragm can couple to the side access port and used to convey the process pressure to a pressure sensor. This isolation diaphragm isolates the sensor from the process fluid. The sensed pressure is related to the level of fluid in the container and measurement circuitry coupled to the sensor can provide an output related to this level.
Some containers which are used to contain process fluid do not have the side access port discussed above for coupling to a pressure sensor. In such a configuration, the only available access port may be located at the top of the container and any level measurements must be performed through this opening.